1. Field of the Invention
The invention is directed to a hydraulic clutch wherein the hydraulic delivery conduits and a portion of the cylinder contain hydraulic fluid after the clutch is deactivated. The invention is particularly well suited for use in a power shift transmission.
2. Description of the Prior Art
Power shift transmissions are provided with a number of hydraulic clutches which are used to engage and disengage different gear settings. Typically, these clutches comprise a plurality of friction and pressure plates that are spring biased into a disengaged position. If it is desired to engage the clutch, hydraulic fluid is applied through a conduit formed in the drive shaft to a piston which is operatively associated with the friction and pressure plates. The friction plates are then forced against the spring into the engaged position for driving a driven member. The piston is provided with small bleed apertures which allow hydraulic fluid to pass through the piston. The bleed apertures are used to reduce centrifugal head caused by the hydraulic fluid contained in the rotating cylinder.
To engage the clutch, the hydraulic delivery conduit and the entire cylinder must be recharged with fluid before the piston can be driven to engage the friction and pressure plates. This sometimes results in unstable shifting characteristics. This is especially true where the oil must be routed through very small conduits.